Introduction to Programming

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Resource Team

R.P Ranjan-Lecturer, SPICTEC, Galle.

W.M.A.S . Wijesekara-Centre manager,CRC Hali-Ela

H.P.U.S Indra Kumara-Instructor,CRC Hanguranketha

R.M.P Bandara-Lecturer,CPICTEC Gurudeniya

K.M.P.U Wimalaweera-Instructor,CRC Polonnaruwa

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What is a computer program?

A computer program is a set of instructions or commands, which tell the computer what to do.

A computer language is a set of symbols and rules used in constructing programs.

Computer languages are used to develop application programs

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Cont….

The machine can understand only the machine language.

Assembly and other high level languages are not machine language.

To transform these languages into machine language, translators are needed.

Source Code Object CodeTranslator

Low Level Language

High Level Language

1st Generation

2nd Generation

3rd Generation

4th Generation

5th Generation

Computer Language

Classification of Programming Languages

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Generation of programming languages

1st Generation language ( 1GL )

2nd Generation languages( 2GL )

3rd Generation languages ( 3GL )

4th Generation languages ( 4GL )

5th Generation languages ( 5GL )

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1st Generation language ( 1GL )

Machine level programming language

Machine code is the binary digit language

It consists of 1s and 0s.

The machine can directly execute the machine code

Execution is speedy because no translators are used.

It is very difficult to write and modify programs.

It is machine dependant, because machine-language instructions vary according to computer architecture.

It is a low level language

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2nd Generation languages( 2GL )

Assembly language is used

Assembler is used to convert assembly language to machine language

Mnemonics and variables are used to write codes

It is a machine dependant language

Difficult to write and modify programs

It is a low level language

Execution is fast

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3rd Generation languages ( 3GL )

It is easy to understand, because it is similar to human languages

Translators are used to convert high level language to machine language

Compilers or interpreters are used as translators.

Some of the 3rd generation languages are unstructured languages such as Basic

It is easy write and modify programs

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3rd Generation languages ( 3GL )

many of the third generation languages are procedural languages because the program instructions comprise a list of steps or procedures

They are not machine dependent languages

One instruction in a third generation language can replace many assembly language instructions

programmer has to describe how it should be done.

Ex : Basic, Fortran, Cobol, Pascal

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4th Generation languages ( 4GL )

Introduced in the late 1980s

They are designed to reduce programming effort

It consumes less time to write a program

They are non procedural languages

Very easy to write and modify

One instruction in 4GL can replace a number of 3GL instructions

Programmer has to describe what is to be done.

4GL languages reduce software development cost.

They are described as application development without programmers

Ex : FOCUS, IDEAL, dbase III plus

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5th Generation languages ( 5GL )

Introduced in the early 1990s

User-friendly Graphical User Interfaces are facilitated.

Very easy to write and modify program

Execution speed is low

Event driven programs were introduced

Ex: Visual basic, Visual C++, Small Talk

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Low Level Languages

First and second generation languages are considered low level languages.

They are machine dependant languages

These languages are close to the hardware

The programmer should have hardware knowledge to write a program

Productivity is low

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High Level Languages

3GL,4GL and 5GL are considered high level languages

They are machine independent languages

It is easy to write and modify

The programmer does not need knowledge of hardware to write programs

Productivity is high

Consume less time to write programs

5GL allow user-friendly facilities

Translators need to be used to convert to machine language

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Translators

Translator is used to convert source code into object code. these are of three types

1.      Assembler

2.      Interpreter

3.      Compiler

Source Code Object CodeTranslator

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Assembler

is a low-level language Translator.

is a software program that converts assembly language into machine language.

converts mnemonics into machine code

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Interpreter

is a translator that goes through the process of translation every time the program is run.

is found running some versions of BASIC, where it translates one line of the program at a time.

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Compiler

is a translator of high level languages

converts a whole program into machine language at once

translates source code into Object Code. This Object code is used to execute whenever it is run

Recompiling required if any changes of source code